1. Field of the Invention
This invention is concerned with unstacking of flat objects with a view to removing them one by one from a stack and carrying out unitary distribution of such objects.
The flat objects considered may in particular be pieces of mail such as envelopes.
An unstacking device permits automatic feeding of a machine for indexing, re-addressing and/or sorting pieces of mail.
2. Description of the Prior Art
In accordance with known practice, a device for unstacking flat objects such as pieces of mail or envelopes essentially comprises a magazine for storing envelopes in a stack and a discharge head located at the end of a magazine. The discharge head is provided with means for suction and transfer of the end envelope of the stack. The magazine itself is equipped with means for displacing the stacked objects towards the discharge head and means for suitable presentation of the end envelope in front of the discharge head.
By way of example, the discharge head can consist of a suction cup subjected to a rocking movement which advantageously takes place on a forward and return path of travel as well as to a back-and-forth movement of translation, an abutment member being associated with the suction cup for the abutting application of the end envelope before this latter is removed from the stack. The discharge head can also consist of a wall having suction orifices and associated with a drum for accelerating the envelope. Said head can also consist of a conveyor-belt or an accelerating suction drum.
The means with which the storage magazine is equipped for ensuring suitable presentation of objects opposite to the discharge head are expected to satisfy many requirements, particularly in regard to the constraints imposed when processing pieces of mail having characteristics which may be very different from each other. Among the constraints which are to be taken into account, the following are in fact worthy of mention:
disparity both in weight and in size of the envelopes of a batch to be processed;
disparity in the characteristics of mail material which can be of paper or of plastic, for example, and results in pieces of mail such as envelopes having surfaces which may be rough, porous, glossy or very smooth;
disparity in constitution or consistency of mail envelopes and the like which can range from a single folded sheet having sealing points or a simple reply card to lined envelopes or documents mailed in band-type wrappers or in wrapping and/or addressing film.
It must consequently be ensured that, as the pieces of mail such as envelopes advance towards the discharge head, the means for presenting the envelopes in front of the head must carry out in particular lateral jogging of the envelopes which have to be aligned on one of their edges at least in the terminal zone of the stack as well as separation of the envelopes from each other in the same terminal zone. This enables the discharge head to perform reliable and correct gripping of the end envelope but of this envelope alone irrespective of the characteristics of the end envelope and those of the envelopes which follow.
The presentation system can comprise a joggable lateral edge guide on the magazine and sets of rollers which are mounted in the bottom wall of the magazine and driven in rotation so as to thrust the envelopes against the joggable lateral edge guide. Said presentation system can also be provided with means for blowing air jets onto the free edges of the envelopes, in particular the top edges of said envelopes, in order to separate the envelopes in the terminal zone of the stack and/or to retain the envelope which follows the end envelope to be withdrawn from the stack.
In order to improve the presentation of envelopes in front of the discharge head and to facilitate withdrawal of the end envelope alone, the magazine can also be equipped with means for tilting the envelopes in its terminal zone so that the end envelope arrives with its bottom edge foremost against the abutment member or the suction wall of the discharge head. These last-mentioned means can be constituted by a set of motor-driven belts or a blowing ramp which produces action on the bottom edges of the envelopes in said terminal zone.
This system for the presentation of objects and especially pieces of mail such as envelopes in front of the discharge head fails to produce consistent action on the different envelopes of a batch to be processed and results in performances which remain insufficient when the envelopes to be processed have a particularly broad spectrum of characteristics.
The aim of the present invention is to provide a device for unstacking objects which may have very different characteristics with respect to each other. By making use of simple means providing highly reliable operation, the device in accordance with the invention permits the achievement of particularly enhanced performances.